A method for reducing defects in the first billet of a casting.

Abstract

This application relates to the field of continuous casting technology and discloses a control method for reducing defects in the first billet of a cast billet. The control method includes: obtaining parameters for the initial cold charge; selecting circular cold charge wafers based on these parameters; obtaining the amount of initial cold charge added; adding circular cold charge wafers to the crystallizer according to this amount and accumulating them to a preset thickness; obtaining the target casting speed for the steel grade of the billet; starting casting; accelerating the casting speed to the target speed before the first billet length reaches a first preset threshold; and activating electromagnetic stirring when the first billet length reaches a second preset threshold. This application effectively reduces oxide defects formed during the rolling process by incorporating initial cold charge into the billet surface during the rolling process. This solves the technical problem in the prior art where defects in the first billet wafer and protective slag prevent the quality from reaching the normal billet level, leading to product downgrading or scrapping and increased costs.

Description

Technical Field

[0001] This application relates to the field of continuous casting technology, and in particular, to a method for controlling defects in the first billet of a casting. Background Technology

[0002] The first billet refers to the first billet after the head is removed in the casting cycle. During the initial casting process, cold material needs to be added to the crystallizer to cool the molten steel and prevent leakage. However, the added cold material will fall off and adhere to the fan-shaped rollers, pressing into the surface of the billet and forming oxide defects during the rolling process. At the same time, the initial casting process is an unsteady casting process with large fluctuations in the liquid level in the crystallizer, which can easily cause the entrapment of protective slag. Therefore, if the initial casting coil has quality problems, it will cause the product to be downgraded or scrapped, resulting in increased costs. Summary of the Invention

[0003] The purpose of this application is to provide a method for controlling defects in the first blank of a cast billet, thereby solving the technical problem in the prior art where defects such as cold material pressing into the first blank and protective slag prevent the quality from reaching the level of a normal cast billet, leading to product downgrading or scrapping and increased costs.

[0004] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0005] According to one aspect of the embodiments of this application, a control method for reducing defects in the first billet of a cast billet is provided. The control method includes: acquiring parameters for the initial casting cold material, selecting a disc cold material according to the parameters; acquiring the amount of initial casting cold material added, adding the disc cold material to a crystallizer according to the amount of initial casting cold material added, and accumulating the disc cold material to a preset thickness; acquiring a target casting speed for the steel grade of the cast billet, starting the casting of the billet, accelerating the casting speed to the target casting speed before the casting length of the first billet reaches a first preset threshold; and activating electromagnetic stirring when the first billet reaches a second preset threshold length.

[0006] In some embodiments, after obtaining the amount of cold material added during initial casting, adding the disc cold material to the crystallizer according to the amount of cold material added during initial casting, and accumulating the disc cold material to a preset thickness, the method further includes: starting the casting of molten steel, canceling the initial casting slag addition process, raising the temperature of the molten steel to a set temperature value, and adding protective slag.

[0007] In some embodiments, before accelerating the billet casting speed to the target casting speed, the method further includes: keeping the tundish submersible nozzle immersed in the molten steel in the crystallizer, and controlling the height difference between the tundish submersible nozzle and the molten steel surface in the crystallizer to a first preset difference value.

[0008] In some embodiments, after accelerating the billet casting speed to the target casting speed, the method further includes: keeping the tundish submersible nozzle immersed in the molten steel in the crystallizer, and controlling the height difference between the tundish submersible nozzle and the molten steel surface in the crystallizer to a second preset difference value.

[0009] In some embodiments, before accelerating the billet casting speed to the target casting speed, the method further includes: controlling the argon flow rate of the stopper rod and the argon flow rate of the inlet to a first flow rate value, and controlling the argon flow rate between plates to a second flow rate value.

[0010] In some embodiments, after accelerating the billet casting speed to the target casting speed, the method further includes: controlling the argon flow rate of the stopper rod and the argon flow rate of the inlet to a third flow rate value, and controlling the argon flow rate between plates to a fourth flow rate value.

[0011] In some embodiments, the parameters of the cold-casting slurry include the diameter, thickness, and density of the disc cold-casting slurry, wherein the diameter is 1-2 cm, the thickness is less than 2 mm, and the density is greater than 8 kg / cm³. 3 .

[0012] In some embodiments, the amount of cold slurry added during initial casting is 7-12 kg / m based on the cross-section of the billet, and the preset thickness is 3-5 mm.

[0013] In some embodiments, the first preset threshold is 5m.

[0014] In some embodiments, the second preset threshold is 8-12m.

[0015] Compared with the prior art, the significant advantages of the technical solution of this application are as follows: by improving the type, amount, and start-up time of the electromagnetic stirring of the second cooling stage, the oxide defects formed during the rolling process of the cold material being pressed into the billet surface are effectively reduced. In addition, by controlling the variable casting speed time, improving the initial casting temperature and optimizing the immersion depth, eliminating the initial casting slag, and optimizing the flow rate of the three argon gas in the tundish to reduce the defects of the initial casting billet, the defects of the protective slag can be well controlled within 5m, which can be removed during the normal billet cutting process. This solves the problems of oxide defects caused by the cold material being pressed into the billet surface and defects caused by the entrapment of protective slag in the prior art, and effectively reduces the problems of product downgrading and scrapping and increased costs caused by defects in the billet.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0017] The above and other features and advantages of this application will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0018] Figure 1A flowchart of a control method for reducing defects in the headstock of a cast billet according to an embodiment of this application is shown. Detailed Implementation

[0019] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0020] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0021] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0022] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0023] The technical solutions of the embodiments of this application are briefly described below:

[0024] According to some embodiments, such as Figure 1 As shown, this application provides a method for controlling defects in the first-end of a cast billet, the method comprising:

[0025] Step 101: Obtain the parameters for cold slurry before casting, and select circular cold slurry according to the parameters for cold slurry before casting;

[0026] Step 102: Obtain the amount of cold material added during initial casting; add the disc cold material to the crystallizer according to the amount of cold material added during initial casting; and stack the disc cold material to a preset thickness.

[0027] Step 103: Obtain the target casting speed for the steel grade of the billet. Casting of the billet begins. Before the casting length of the first billet reaches the first preset threshold, the casting speed of the billet is accelerated to the target casting speed.

[0028] Step 104: When the first billet is cast to the second preset threshold length, electromagnetic stirring is started.

[0029] Based on the above embodiments, in step 101, the parameters for the cold casting slurry include the diameter, thickness, and density of the disc cold casting slurry. The diameter, thickness, and density of the disc cold casting slurry can be set according to actual requirements. In some embodiments, the diameter is set to 1-2 cm, the thickness is set to <2 mm, and the density is set to >8 kg / cm³. 3 The appropriate type of cold-pressed disc should be selected based on its diameter, thickness, and density.

[0030] In step 102, the amount of cold slug added at the start of casting can be set according to actual needs. In some embodiments, the amount of cold slug added at the start of casting is set to 7-12 kg / m of the billet cross-section, where m is the width of the billet cross-section and kg is the mass of the cold slug, which is the mass of the disc cold slug. Therefore, the operation step is to add disc cold slugs into the crystallizer at 7-12 kg / m of the billet cross-section. The preset thickness can be set according to actual needs. In some embodiments, the preset thickness is set to 3-5 mm.

[0031] In step 103, the first preset threshold can be set according to actual needs. In some embodiments, the first preset threshold is 5m. During the casting process, the variable casting speed acceleration is adjusted according to the target casting speed of the steel grade, and the time for the casting speed to rise to the target casting speed must be controlled within the casting length < 5m.

[0032] In step 104, the second preset threshold can be set according to actual needs. In some embodiments, the second preset threshold is set to 8-12m. During operation, the secondary cooling electromagnetic stirring (S-EMS) is started when the billet head is cast to 8-12m.

[0033] By improving the type and amount of cold material added during the initial casting and the start-up time of the electromagnetic stirring during the secondary cooling process, the oxide defects formed during the rolling process of the cold material pressed into the surface of the billet are effectively reduced. This solves the technical problem in the existing technology where the cold material is pressed into the billet head and the protective slag defects prevent the quality from reaching the level of a normal billet, leading to product downgrading or scrapping and increased costs.

[0034] To enable those skilled in the art to better understand this application, the following will be combined with Figure 1 The details of this application are described in detail.

[0035] According to some embodiments, in step 102, after obtaining the amount of cold slurry added during initial casting, adding the disc cold slurry to the crystallizer according to the amount of cold slurry added during initial casting, and stacking the disc cold slurry to a preset thickness, the method further includes:

[0036] Step 1021: Start pouring molten steel, cancel the process of adding slag during pouring, raise the temperature of the molten steel to the set temperature value, and add protective slag.

[0037] Based on the above embodiments, the set temperature value can be set according to actual needs. In some embodiments, the set temperature value is set to 5-10℃. The function of adding the initial pouring slag is to increase the surface temperature of the molten steel, which is beneficial to the melting of the protective slag. This application eliminates the need for the initial pouring slag and replaces the process of adding the initial pouring slag by increasing the initial pouring temperature of the molten steel by 5-10℃. This reduces the slag entrapment defects caused by the initial pouring slag during the initial pouring process. At the same time, increasing the initial pouring temperature by 5-10℃ ensures the melting of the protective slag.

[0038] According to some embodiments, before accelerating the billet casting speed to the target casting speed, the method further includes:

[0039] Keep the tundish submersible nozzle immersed in the molten steel in the crystallizer, and control the height difference between the tundish submersible nozzle and the molten steel level in the crystallizer to a first preset difference value.

[0040] Based on the above embodiments, the first preset difference can be set according to actual needs. In some embodiments, the first preset difference is set to 110mm-130mm, that is, before the billet casting speed is accelerated to the target casting speed, the depth of the immersion nozzle in the molten steel is 110mm-130mm.

[0041] According to some embodiments, after accelerating the billet casting speed to the target casting speed, the method further includes:

[0042] Keep the tundish submersible nozzle immersed in the molten steel in the crystallizer, and control the height difference between the tundish submersible nozzle and the molten steel level in the crystallizer to a second preset difference value.

[0043] Based on the above embodiments, the second preset difference can be set according to actual needs. In some embodiments, the second preset difference is set to 140-170mm, that is, after the billet casting speed is accelerated to the target casting speed, the depth of the immersion nozzle in the molten steel is 140-170mm.

[0044] Before the billet casting speed is accelerated to the target casting speed, the height difference between the tundish submersible nozzle and the molten steel surface in the crystallizer is small. At this time, the tundish submersible nozzle is immersed to a shallow depth. Since the molten steel opening temperature is increased by 5-10℃, the shallow immersion depth of the tundish submersible nozzle is conducive to increasing the surface temperature of the molten steel and is conducive to the melting of the protective slag.

[0045] After the billet casting speed is accelerated to the target speed, the protective slag has melted, which can increase the immersion depth of the tundish submerged entry nozzle and control slag entrapment. Therefore, the height difference between the tundish submerged entry nozzle and the molten steel surface in the crystallizer becomes larger.

[0046] According to some embodiments, before accelerating the billet casting speed to the target casting speed, the method further includes:

[0047] The argon flow rate of the stopper rod and the argon flow rate of the inlet are controlled at the first flow rate value, and the argon flow rate between the plates is controlled at the second flow rate value.

[0048] Based on the above embodiments, the first flow rate value can be set according to actual needs. In some embodiments, the first flow rate value is set to 1-2 L / min, that is, before accelerating the billet casting speed to the target casting speed, the stopper rod argon flow rate is set to 1-2 L / min, and the upper nozzle argon flow rate is set to 1-2 L / min. The second flow rate value can be set according to actual needs. In some embodiments, the second flow rate value is set to 2-3 L / min, that is, before accelerating the billet casting speed to the target casting speed, the interplate argon flow rate is set to 2-3 L / min.

[0049] According to some embodiments, after accelerating the billet casting speed to the target casting speed, the method further includes:

[0050] The argon flow rate of the stopper rod and the argon flow rate of the inlet are controlled at the third flow rate value, and the argon flow rate between the plates is controlled at the fourth flow rate value.

[0051] Based on the above embodiments, the third flow rate value can be set according to actual needs. In some embodiments, the third flow rate value is set to 3-5 L / min, that is, after the billet casting speed is accelerated to the target casting speed, the stopper rod argon flow rate is set to 3-5 L / min, and the upper nozzle argon flow rate is set to 3-5 L / min. The fourth flow rate value can be set according to actual needs. In some embodiments, the fourth flow rate value is set to 3-4 L / min, that is, after the billet casting speed is accelerated to the target casting speed, the interplate argon flow rate is set to 3-4 L / min.

[0052] This application selects circular cold material in the shape of a disc to reduce the amount of cold material pressed into the surface of the billet, thus reducing surface defects. The amount of cold material added is optimized to 7-12 kg / m of cross-section, with a thickness controlled at 3-5 mm. The time to reach the target casting speed during the initial pouring process is controlled within a casting length of <5 m, reducing the length of the unsteady billet. The addition of initial pouring slag is eliminated, and the molten steel temperature is increased by 3-5℃ to reduce slag entrapment defects caused by slag during the initial pouring process, while increasing the temperature to ensure the melting of the protective slag. The immersion depth control of the submerged entry nozzle is optimized, selecting different immersion depths for different pouring times to ensure both the melting effect of the protective slag and the control of slag entrapment. Argon flow rate is adjusted, with staged control to ensure an active crystallizer surface and slag entrapment control. The start time of the secondary cooling electromagnetic stirring is adjusted, starting the stirring after 8-12 m of billet pouring to reduce the initial pouring cold material being attracted to the rollers by electromagnetic force and pressed into the billet surface, while also suppressing fluctuations in the crystallizer surface during the initial pouring process. This method for controlling defects in the first blank of a cast billet can effectively reduce defects in the first blank of a cast billet and improve the quality of the cast billet.

[0053] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0054] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for controlling defects in the first billet of a casting, characterized in that, The control method includes: Obtain the parameters for cold slurry before casting, and select circular cold slurry based on the parameters. Obtain the amount of cold material added during initial casting, add the disc cold material to the crystallizer according to the amount of cold material added during initial casting, and stack the disc cold material to a preset thickness; After that, the molten steel is poured, the initial slag addition process is cancelled, the temperature of the molten steel is raised to the set temperature value, and protective slag is added; Once the target casting speed for the steel grade of the billet is obtained, the billet casting begins. Before the first billet casting length reaches the first preset threshold, the casting speed of the billet is accelerated to the target casting speed. When the first billet reaches the second preset threshold length, electromagnetic stirring is activated. The parameters for the cold material to be poured include the diameter, thickness, and density of the disc cold material; The diameter is 1-2 cm, the thickness is less than 2 mm, and the density is greater than 8 kg / cm³. 3 .

2. The method according to claim 1, characterized in that, Before accelerating the casting speed to the target casting speed, the method further includes: Keep the tundish submersible nozzle immersed in the molten steel in the crystallizer, and control the height difference between the tundish submersible nozzle and the molten steel level in the crystallizer to a first preset difference value.

3. The method according to claim 2, characterized in that, After accelerating the casting speed to the target casting speed, the method further includes: Keep the tundish submersible nozzle immersed in the molten steel in the crystallizer, and control the height difference between the tundish submersible nozzle and the molten steel level in the crystallizer to a second preset difference value.

4. The method according to claim 1, characterized in that, Before accelerating the casting speed to the target casting speed, the method further includes: The argon flow rate of the stopper rod and the argon flow rate of the inlet are controlled at the first flow rate value, and the argon flow rate between the plates is controlled at the second flow rate value.

5. The method according to claim 4, characterized in that, After accelerating the casting speed to the target casting speed, the method further includes: The argon flow rate of the stopper rod and the argon flow rate of the inlet are controlled at the third flow rate value, and the argon flow rate between the plates is controlled at the fourth flow rate value.

6. The method according to claim 1, characterized in that, The amount of cold slurry added during initial casting is 7-12 kg / m based on the cross-section of the billet, and the preset thickness is 3-5 mm.

7. The method according to claim 1, characterized in that, The first preset threshold is 5m.

8. The method according to claim 1, characterized in that, The second preset threshold is 8-12m.

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